The present invention relates to the design and construction of a valve mechanism for controlling fluid flow through the damping system of a suspension system. More particularly, the present invention relates to damping system having an inertia-activated compression fluid flow control mechanism in combination with a pressure-activated compression fluid flow control mechanism for use in the suspension system of a vehicle, and particularly for use in a suspension system for a pedal-driven vehicle.
Suspension systems are used for various applications, such as for cushioning impacts, vibrations, or other disturbances experienced in the operation of vehicles and machinery. A telescoping suspension system typically has at least one telescoping strut comprising two telescoping members maintained in a biased-apart, neutral configuration. The telescoping members are telescopingly and coaxially engaged, and move together when the system is compressed in response to a force input and apart when the system rebounds or expands after compression. A common application of a suspension system is in bicycles and motorcycles for cushioning impacts or vibrations experienced by the rider when the bicycle or motorcycle is ridden over bumps, ruts, rocks, pot holes, or other obstacles.
Damping systems have been provided in suspension systems in order to absorb at least a portion of the energy imparted to the system as a result of impacts, vibrations, or other disturbances, as well as to provide desirable speed-sensitive or force-sensitive qualities to the suspension system. The design of such damping systems depends upon several factors. In bicycles, for example, the degree of damping to be achieved depends on several variables including the speed of the bicycle, the terrain over which the bicycle is being ridden, the structure of the bicycle, the wheel width, and the weight of the rider.
A particular concern in the design of damping systems for vehicles, and especially for pedal-driven vehicles such as bicycles, is the effect of the damping system on force inputs such as pedal force inputs. In bicycles, for example, riders frequently pedal while standing out of the saddle (rather than sitting), using their weight in addition to muscle force to propel the bicycle. This technique is particularly useful, for example, for accelerating quickly and for negotiating inclines. During out-of-saddle pedalling, however, a bicycle having a suspension system tends to bob down and up as the pedals are forced down and up by the rider's pedalling efforts and accompanying weight shift. This bobbing effect is exacerbated by a supple or soft suspension system, and may occur, in a pedal-driven vehicle having a very soft suspension, even when the rider is pedalling sitting down. The result is that an often significant portion of the energy being imparted to the bicycle by the rider to propel it forward is instead being absorbed by the damping system of the suspension.
Accordingly, there is a need for a suspension system for vehicles, and particularly for pedal-driven vehicles such bicycles, that resists the absorption of energy imparted to the system as a result of, for example, pedalling out of the saddle, yet permits adequate shock absorption in all regimes in which such vehicles are used.